Method for manufacturing gallium oxide based substrate, light emitting device, and method for manufacturing the light emitting device

ABSTRACT

A light emitting device comprises a gallium oxide based substrate, a gallium oxynitride based layer on the gallium oxide based substrate, a first conductivity-type semiconductor layer on the gallium oxynitride based layer, an active layer on the first conductivity-type semiconductor layer, and a second conductivity-type semiconductor layer on the active layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/620,061 filed on Nov. 17, 2009 now U.S. Pat. No. 8,125,001 claimingthe benefit of Korean Patent Application No. 10-2008-0114144 filed onNov. 17, 2008, both of which are hereby incorporated by reference forall purpose as if fully set forth herein.

BACKGROUND

The present disclosure relates to a method for manufacturing a galliumoxide based substrate, a light emitting device, and a method formanufacturing the light emitting device.

Nitride semiconductors attract a great attention in the optical deviceand high-power electronic device development fields because of theirhigh thermal stability and wide bandgap energy. In particular, blue,green and UV light emitting devices using nitride semiconductors havebeen commercialized and widely used.

Nitride semiconductor light emitting devices include a nitridesemiconductor layer that is organic-chemically deposited over a sapphiresubstrate being a dissimilar substrate.

The sapphire substrate has an electrically insulating characteristic.Thus, in order to apply a voltage to the nitride semiconductor layer, itis necessary to partially etch the nitride semiconductor layer or removethe sapphire substrate.

The nitride semiconductor light emitting devices may be classified intolateral type nitride semiconductor light emitting devices and verticaltype nitride semiconductor light emitting devices according to positionof an electrode layer.

In the case of the lateral type nitride semiconductor light emittingdevices, a nitride semiconductor layer is formed over the sapphiresubstrate, and two electrode layers are formed to be arranged over thenitride semiconductor layer.

In the case of the vertical type nitride semiconductor light emittingdevices, a nitride semiconductor layer is formed over the sapphiresubstrate, the sapphire substrate is separated from the nitridesemiconductor layer, and two electrode layers are formed to be arrangedon and under the nitride semiconductor layer, respectively.

Meanwhile, the lateral type nitride semiconductor light emitting devicesneed to remove a portion of the nitride semiconductor layer in order toform two electrode layers, and has limitations in that the reliabilityand efficiency of light emission characteristic are degraded because ofnon-uniform current distribution.

Furthermore, the vertical type nitride semiconductor light emittingdevices need to separate the sapphire substrate.

Therefore, many researches have been made on vertical type nitridesemiconductor light emitting devices, in particular, nitridesemiconductor light emitting devices that need not separate thesubstrate by the use of conductive substrates.

SUMMARY

Embodiments provide a method for manufacturing a gallium oxide basedsubstrate, a light emitting device, and a method for manufacturing thelight emitting device.

Embodiments provide a method for manufacturing a gallium oxide basedsubstrate, which is capable of forming a high-quality nitridesemiconductor layer, a light emitting device, and a method formanufacturing the light emitting device.

In an embodiment, a light emitting device comprises: a gallium oxidebased substrate; a gallium oxynitride based layer on the gallium oxidebased substrate; a first conductivity-type semiconductor layer on thegallium oxynitride based layer; an active layer on the firstconductivity-type semiconductor layer; and a second conductivity-typesemiconductor layer on the active layer.

In an embodiment, a method for manufacturing a gallium oxide basedsubstrate comprises: preparing a gallium oxide based substrate; andperforming a thermal treatment on the gallium oxide based substrate inan oxygen atmosphere.

In an embodiment, a method for manufacturing a light emitting devicecomprises: preparing a gallium oxide based substrate; forming a galliumoxynitride based layer on the gallium oxide based substrate; forming afirst conductivity-type semiconductor layer on the gallium oxynitridebased layer; forming an active layer on the first conductivity-typesemiconductor layer; and forming a second conductivity-typesemiconductor layer on the active layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view for explaining a method for manufacturing agallium oxide based substrate, and a light emitting device manufacturedby a method for manufacturing a light emitting device according to anembodiment.

FIG. 2 is a flowchart illustrating a method for manufacturing a lightemitting device according to an embodiment.

FIG. 3 is a diagram for explaining surface scratches of a gallium oxidebased substrate.

FIGS. 4 and 5 are diagrams for explaining the surface of the galliumnitride based layer grown to 100 nm thick on the scratched gallium oxidebased substrate.

FIG. 6 illustrates the surface of the gallium oxide based substrateafter the thermal treatment is performed on the gallium oxide basedsubstrate in an oxygen atmosphere.

FIG. 7 illustrates the surface of the gallium nitride based layer grownto 100 m thick on the gallium oxide based substrate that has beenthermally treated in an oxygen atmosphere.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings.

In the description of embodiments, it will be understood that when alayer (or film), region, pattern or structure is referred to as being‘another’ layer (or film), region, pad or pattern, the terminology of“on” and “under” includes both the meanings of ‘directly’ and‘indirectly’. Further, the reference about ‘on’ and ‘under’ each layerwill be made on the basis of drawings.

In the drawings, the thickness or size of each layer is exaggerated,omitted, or schematically illustrated for convenience in description andclarity. Also, the size of each element does not entirely reflect anactual size.

FIG. 1 is a sectional view for explaining a method for manufacturing agallium oxide based substrate, and a light emitting device manufacturedby a method for manufacturing a light emitting device according to anembodiment.

Referring to FIG. 1, a first conductivity-type semiconductor layer 20,an active layer 30, and a second conductivity-type semiconductor layer40 are formed on a gallium oxide based substrate 10. A first electrodelayer 50 is disposed under the gallium oxide based substrate 10, and asecond electrode layer 60 is disposed on the second conductivity-typesemiconductor layer 40.

Furthermore, a gallium oxynitride based layer 11 may be formed betweenthe gallium oxide based substrate 10 and the first conductivity-typesemiconductor layer 20.

The gallium oxide based substrate 10 may be formed of gallium oxide(Ga₂O₃) and may have excellent electrical conductivity due to impuritydoping.

Also, the gallium oxide based substrate 10 may be formed of one of(InGa)₂O₃, (AlGa)₂O₃, or (InAlGa)₂O₃.

The first conductivity-type semiconductor layer 20 may be an n-typesemiconductor layer. For example, the first conductivity-typesemiconductor layer 20 may be a gallium nitride (GaN) based layer intowhich n-type impurities are doped.

Also, the n-type semiconductor layer may be formed of one of InGaN,AlGaN, InAlGaN, AlInN, AlGaN/GaN SPS (short-period superlattice), orAlGaN/AlGaN SPS (short-period superlattice) into which n-type impuritiesare doped.

The active layer 30 is a layer in which electrons and holes from thefirst conductivity-type semiconductor layer 20 and the secondconductivity-type semiconductor layer 40 are recombined to emit light.The active layer 30 may include a barrier layer and a well layer. Forexample, the active layer 30 may be a gallium nitride layer or anindium-containing gallium nitride layer.

Also, the active layer 30 may be formed of one of InGaN/GaN,InGaN/InGaN, or InGaN/AlGaN.

The second conductivity-type semiconductor layer 40 may be a p-typesemiconductor layer. For example, the second conductivity-typesemiconductor layer 40 may be a gallium nitride based layer into whichp-type impurities are doped.

Also, the p-type semiconductor layer may be formed of one of InGaN,AlGaN, InAlGaN, AlInN, AlGaN/GaN SPS (short-period superlattice), orAlGaN/AlGaN SPS (short-period superlattice) into which n-type impuritiesare doped.

The first electrode layer 50 and the second electrode layer 60 may beformed of a conductive material such as a metal.

The structure of the light emitting device illustrated in FIG. 1 ismerely exemplary, and the present invention is not limited thereto. Inmanufacturing the light emitting device, another semiconductor layerthat is not described in FIG. 1 may be further included between thesemiconductor layers illustrated in FIG. 1. For example, an n-typesemiconductor layer may further be formed between the secondconductivity-type semiconductor layer 40 and the second electrode layer60.

Meanwhile, gallium oxide is thermodynamically unstable and mechanicallyvulnerable at high temperature.

The crystal structure of gallium oxide is a monoclinic system and has astrong cleavage characteristic with respect to a specific crystal plane,that is, (100) plane and (001) plane. Thus, when gallium oxide ismanufactured in a thin film form, layers are easily separated and thesurface treatment is difficult.

Therefore, in accordance with an embodiment, the gallium nitride basedlayer can be grown on the gallium oxide based substrate 10 into ahigh-quality thin film through the surface treatment of the galliumbased de substrate 10.

FIG. 2 is a flowchart illustrating a method for manufacturing a lightemitting device according to an embodiment.

Referring to FIG. 2, a gallium oxide based substrate 10 is prepared(S100). The gallium oxide based substrate 10 may be a gallium oxidebased substrate into which first conductivity-type impurities such assilicon (Si) are doped in order to improve the electrical conductivity.

A wet cleaning is performed on the gallium oxide based substrate 10 toremove organic material or inorganic material remaining on the galliumoxide based substrate 10. For example, in the wet cleaning, an acidcleaning may be performed after an organic cleaning.

The organic cleaning is to remove foreign materials from the galliumoxide based substrate 10 by using acetone and methanol, and the acidcleaning is to remove gallium oxide particles existing on the galliumoxide based substrate 10 in a protrusion shape by using fluoric acid,sulfuric acid, and hydrogen peroxide.

For example, as the organic cleaning method, the gallium oxide basedsubstrate 10 is dipped into acetone and methanol, an ultrasonic cleaningis performed for three minutes, and then, an ultrasonic cleaning isperformed with deionized water for three minutes.

Meanwhile, the gallium oxide based substrate 10 is made by mechanicallycut gallium oxide crystal ingot into a predetermined size and in apredetermined crystal direction. Therefore, surface scratch is formed onthe surface of the gallium oxide based substrate 10 during the cuttingprocess.

FIG. 3 is a diagram for explaining surface scratches of the galliumoxide based substrate. It can be seen from FIG. 3 that many surfacescratches 15 occur in the gallium oxide based substrate 10.

If the gallium nitride based layer is formed on the gallium oxide basedsubstrate 10 with the surface scratches 15, a high-quality galliumnitride based layer cannot be obtained. Such surface scratches 15 arenot removed by the wet cleaning.

FIGS. 4 and 5 are diagrams for explaining the surface of the galliumnitride based layer 23 grown to 100 nm thick on the scratched galliumoxide based substrate.

FIG. 4 illustrates a gallium nitride based pattern 21 having a differentphase from its periphery and having a protrusion shape on the surface ofthe gallium nitride based layer 23, and FIG. 5 illustrates a galliumnitride based pattern 22 having a valley-like recessed shape on thesurface of the gallium nitride based layer 23 because the growth rate isretarded compared with its periphery.

As illustrated in FIGS. 4 and 5, the surface shape of the galliumnitride based layer 23 is determined according to the shape of thesurface scratches of the gallium oxide based substrate 10.

Meanwhile, in order to grow the high-quality gallium nitride based layeron the gallium oxide based substrate 10, it is necessary to remove thesurface scratches 15 of the gallium oxide based substrate 10.

Referring again to FIG. 2, according to the embodiment, the thermaltreatment is performed on the gallium oxide based substrate 10 in anoxygen atmosphere in order to remove the surface scratches occurring onthe surface of the gallium oxide based substrate 10.

That is, an oxygen gas or mixed gas containing oxygen gas as a main gasis injected into a chamber, and the thermal treatment is performed onthe gallium oxide based substrate 10 at a temperature of 900-1400° C.for three minutes to three hours. In this case, when the thermaltreatment temperature is high, the thermal treatment is performed for ashort time. On the contrary, when the thermal treatment temperature islow, the thermal treatment is performed for a long time.

For example, according to a method of performing the thermal treatmentin the oxygen atmosphere, the gallium oxide based substrate 10 is putinto the chamber, and the temperature of the chamber is increased to1100° C. while supplying high-purity oxygen gas into the chamber at aflow rate of 5 slm, and then, a high-temperature oxygen thermaltreatment is performed for one hour. The wet cleaning may be againperformed on the gallium oxide based substrate 10 that has beenthermally treated in the oxygen atmosphere.

If the thermal treatment is performed on the gallium oxide basedsubstrate 10, atoms on the surface of the gallium oxide based substrate10 are thermally migrated to the most thermally stable position, so thatsurface atoms are rearranged. Therefore, the surface scratches 15 of thegallium oxide based substrate 10 can be healed.

Meanwhile, since the melting point of gallium oxide is 1725° C., if thethermal treatment is performed at a temperature higher than 1400° C.,crystal atoms on the surface of the gallium oxide based substrate 10 arethermally molten and evaporated, and thus, the characteristics of thesurface of the gallium oxide based substrate 10 is degraded. If thethermal treatment is performed at a temperature lower than 900° C., thesurface scratches 15 cannot be effectively healed because of a lowmobility of the crystal atoms on the surface of the gallium oxide basedsubstrate 10.

FIG. 6 illustrates the surface of the gallium oxide based substrateafter the thermal treatment is performed on the gallium oxide basedsubstrate in an oxygen atmosphere.

It can be seen from FIG. 6 that when the thermal treatment is performedon the gallium oxide based substrate 10 in an oxygen atmosphere, mostsurface scratches 15 of the gallium oxide based substrate 10 are healedand only slight impressions remain.

FIG. 7 illustrates the surface of the gallium nitride based layer grownto 100 nm thick on the gallium oxide based substrate that has beenthermally treated in an oxygen atmosphere.

Compared with FIGS. 4 and 5, most impressions caused by the surfacescratches on the surface of the gallium nitride based layer 23 areremoved and the gallium nitride based pattern 21 slightly remains.

Referring again to FIG. 2, the thermal treatment is performed on thegallium oxide based substrate 10 in an oxygen atmosphere, and then,high-temperature nitridation treatment is selectively performed on thegallium oxide based substrate 10 in an ammonia atmosphere (S120).

The high-temperature nitridation process may be performed by injectingammonia gas, a mixed gas of ammonia gas and oxygen gas, or a mixed gasof ammonia gas and nitrogen gas into the chamber.

Through the high-temperature nitridation process, a gallium oxynitridebased layer 11 is formed on the gallium oxide based substrate 10. Thegallium oxynitride based layer 11 may serve as a buffer layer of agallium nitride based layer, which will be grown later, and makes itpossible to form a high-quality gallium nitride based layer on thegallium oxide based substrate 10.

In this case, the electrical conductivity of the gallium oxynitridebased layer 11 can be improved by supplying a silicon-containing gassuch as silane gas to the gas injected into the chamber.

Then, a first conductivity-type semiconductor layer 20 is grown on thegallium oxynitride based layer 11 (S130), an active layer 30 is grown onthe first conductivity-type semiconductor layer 20 (S140), and a secondconductivity-type semiconductor layer 40 is grown on the active layer 30(S150).

For example, the first conductivity-type semiconductor layer 20 may beformed by injecting trimethylgallium (TMGa) gas, ammonia gas (NH₃),nitrogen gas (N₂), and silane gas (SiH₄) containing n-type impurity suchas silicon (Si) into the chamber.

Furthermore, the active layer 30 may be formed in a multiple quantumwell structure having InGaN/GaN structure by injecting trimethylgallium(TMGa) gas, ammonia gas (NH₃), nitrogen gas (N₂), and trimethylindium(TMIn) gas.

Moreover, the second conductivity-type semiconductor layer 40 may beformed by injecting trimethylgallium (TMGa) gas, ammonia gas (NH₃),nitrogen gas (N₂), and bis(ethylcyclopentadienyl)magnesium (EtCp₂Mg){Mg(C₂H₅C₅H₄)₂} into the chamber.

A first electrode layer 50 is formed below the gallium oxide basedsubstrate 10, and a second electrode 60 is formed on the secondconductivity-type semiconductor layer 40.

As mentioned above, according to the embodiment, the gallium nitridebased layer grown on the gallium oxide based substrate 10 can be formedwith high quality by the surface treatment of the gallium oxide basedsubstrate 10.

Furthermore, the gallium nitride based layer grown on the gallium oxidebased substrate 10 can be formed with higher quality by forming thegallium oxynitride based layer 11 on the surface of the gallium oxidebased substrate 10.

Moreover, the electrical conductivity of the gallium oxynitride basedlayer 11 can be further improved by injecting the impurities into thegallium oxynitride based layer 11.

By forming the nitride semiconductor layer on the substrate having theelectrical conductivity through those procedures, the vertical typelight emitting devices can be manufactured without removal of thesubstrate.

Embodiments provide a method for manufacturing a gallium oxide basedsubstrate, a light emitting device, and a method for manufacturing thelight emitting device.

Embodiments provide a method for manufacturing a gallium oxide basedsubstrate, which is capable of forming a high-quality nitridesemiconductor layer, a light emitting device, and a method formanufacturing the light emitting device.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A light emitting device, comprising: a galliumoxide based substrate; a first conductivity-type semiconductor layer onthe gallium oxide based substrate; an active layer on the firstconductivity-type semiconductor layer; and a second conductivity-typesemiconductor layer on the active layer, wherein the gallium oxide basedsubstrate contains first conductivity-type impurities.
 2. The lightemitting device according to claim 1, further comprising a galliumoxynitride based layer on the gallium oxide based substrate.
 3. Thelight emitting device according to claim 2, wherein the galliumoxynitride based layer and the gallium oxide based substrate contain thesame conductivity-type impurities.
 4. The light emitting deviceaccording to claim 2, wherein the gallium oxynitride based layercomprises the first conductivity-type impurities.
 5. The light emittingdevice according to claim 1, further comprising: a first electrode layerunder the gallium oxide based substrate; and a second electrode layer onthe second conductivity-type semiconductor layer.
 6. The light emittingdevice according to claim 1, wherein the first conductivity-typesemiconductor layer comprises a gallium nitride based layer containingn-type impurities.
 7. The light emitting device according to claim 1,wherein the second conductivity-type semiconductor layer comprises agallium nitride based layer containing p-type impurities.
 8. The lightemitting device according to claim 1, wherein the active layer comprisesa gallium nitride based layer.
 9. The light emitting device according toclaim 1, wherein the active layer is an indium-containing galliumnitride based layer.
 10. The light emitting device according to claim 1,wherein a surface of the gallium oxide based substrate is essentiallyfree of scratches.
 11. The light emitting device according to claim 1,wherein the gallium oxide based substrate is formed by performing athermal treatment on the gallium oxide based substrate in an oxygenatmosphere.
 12. A light emitting device, comprising: a gallium oxidebased substrate; a gallium oxynitride based layer on the gallium oxidebased substrate; and a first conductivity-type semiconductor layer onthe gallium oxynitride based layer, wherein the gallium oxynitride basedlayer and the gallium oxide based substrate contain the sameconductivity-type impurities.
 13. The light emitting device according toclaim 12, further comprising an active layer on the firstconductivity-type semiconductor layer; and a second conductivity-typesemiconductor layer on the active layer.
 14. The light emitting deviceaccording to claim 13, wherein the second conductivity-typesemiconductor layer comprises a gallium nitride based layer containingp-type impurities.
 15. The light emitting device according to claim 12,wherein the gallium oxynitride based layer comprises firstconductivity-type impurities.
 16. The light emitting device according toclaim 12, wherein the gallium oxide based substrate contains firstconductivity-type impurities.
 17. The light emitting device according toclaim 12, wherein the first conductivity-type semiconductor layercomprises a gallium nitride based layer containing n-type impurities.18. The light emitting device according to claim 12, wherein a surfaceof the gallium oxide based substrate is essentially free of scratches.19. The light emitting device according to claim 12, wherein the galliumoxide based substrate is formed by performing a thermal treatment on thegallium oxide based substrate in an oxygen atmosphere.